Automatic transmissions, especially for motor vehicles, include, in accord with the state of the technology, planetary gearsets, which are shifted by means of friction elements or shifting elements, such as shifting clutches and brakes and which are normally connected to a start-up element, that is subjected to slip effect and optionally has a converter lock-up clutch, for example a hydrodynamic torque converter or a fluid clutch.
Within the general framework of DE 101 15 983 A1, the applicant, for instance, has described a multi-speed transmission having an input drive shaft, which is connected to an input side planetary gearset, and an output drive shaft, which is connected to an output side planetary gearset. The described multi-speed transmission also has a maximum of seven shifting elements, by means of the selective shifting thereof, seven forward gears can be shifted, without range-shifting. The input side planetary gearset is constructed as a shiftable or a non-shiftable planetary gearset, or alternately, as a maximum of two non-shiftable, mutually coupled planetary gearsets. The output side planetary gearset is designed as a two carrier, four shaft transmission with two shiftable planetary gearsets and four free shafts. The first free shaft of this two carrier, four shaft transmission is bound to the first shifting element, the second free shaft connects with the second and third shifting element, the third free shaft is connected to the fourth and fifth shifting elements and the fourth free shaft is bound with the output drive shaft. In the case of a multi-speed transmission, with six shifting elements, in accord with the invention, it is proposed that the third free shaft or the first free shaft of the output sided planetary gearset should be bound additionally to a sixth shifting element. With a multi-speed transmission having a total of seven shifting elements, in accord with the invention it is proposed, that the third free shaft be connected to sixth shifting element and the first free shaft additionally be connected to a seventh shifting element.
A plurality of other multi-speed transmissions are, for example, also disclosed from in DE 101 15 995 A of the applicant, wherein four shiftable, mutually coupled planetary gearsets and six or seven friction-based shifting elements are provided, by the selective engagement thereof, a speed of rotation of an input drive shaft of the transmission is transferred to an output drive shaft of the transmission, and further nine or eleven forward gears may be implemented and at least one reverse gear stage can be shifted into. Consulting the transmission scheme, it is seen, that in each gear, two or three shifting elements are engaged, whereby, by means of a change from one gear to the next higher or lower gear range shifting is avoided, respectively, by disengaging only one engaged shifting element and retaining in place the previously disengaged shifting element.
Additionally, in the conventionally related, but not yet published patent application, DE 102005002337.1 of the applicant, a multi-speed transmission is proposed. The transmission possesses an input drive shaft, an output drive shaft, four mutually coupled individual planetary gearsets along with five shifting elements, whereby, eight forward gears are implemented without range shifting such, that when changing from one forward gear to the immediately next successive higher or lower forward gear, respectively, only one of the previously engaged shifting elements is disengaged and only one of the previously disengaged shifting elements is engaged. The multi-speed transmission also possesses a reverse gear. In all forward gear and in the single reverse gear, respectively, three shifting elements are engaged.
Considering the kinematic coupling of the four planetary gearsets among each other and the two shafts, namely, for input and output, provision is made, that a carrier of the fourth planetary gearset and the input drive shaft are bound together and form a first shaft of the transmission; a carrier of the third planetary gearset and the output drive shaft are bound together and form a second shaft of the transmission; a sun gear of the first planetary gearset and a sun gear of the fourth planetary gear are connected together to form a third shaft of the transmission; a ring gear of the first planetary gearset forms a fourth shaft of the transmission; a ring gear of the second planetary gearset and a sun gear of the third planetary gearset are bound together and form a fifth shaft of the transmission; a carrier of the first planetary gearset and a ring gear of the third planetary gearset are bound together and form a sixth shift of the transmission; a sun gear of the second planetary gearset and a ring gear of the fourth planetary gearset are bound together and form a seventh shaft of the transmission; and a carrier of the second planetary gearset forms an eighth shaft of the transmission.
Further, considering the kinematic coupling of the fifth shifting element with the four planetary gearsets and on the input and output drive shafts, it is provided that placements are made so that, in the direction of the flow of power, the first shifting element is between the third shaft and the transmission housing; the second shifting element is between the fourth shaft and the transmission housing; the third shifting element is between the first and fifth shafts; the fourth shifting element is either between the eighth and second shafts, or between the eighth and sixth shafts, and the fifth shifting element is either between the seventh and fifth shafts or between the fifth and eighth shafts.
Automatically shiftable vehicle transmissions, which are based on planetary gearsets, have, in general, been described many times in the state of the technology and form the foundation of on-going development and improvement thereof. These transmissions should possess a sufficient number of forward gears along with the usual single reverse gear and provide a very well adapted ratio selection with an advantageous spread. Further, these transmissions enable high acceleration ratios in the forward direction and are suitable for installation both in passenger cars as well as in commercial vehicles. Beyond this, these transmissions should require a relatively small investment of money and labor for assembly, and relatively small number of shifting elements. They should further avoid sequential shifting arrangements requiring double clutching. The result being that when shifting in defined gear-groups, only one shifting element need be operated.